1. Field
A scroll compressor, and more particularly, a scroll compressor capable of preventing frictional loss or abrasion of a wrap is disclosed herein.
2. Background
The scroll compressor is a compressor that forms a compression chamber including a suction chamber, an intermediate pressure chamber, and a discharge chamber between a plurality of scrolls while the plurality of scrolls perform a relative orbiting motion in an engaged state. Such a scroll compressor may obtain a relatively high compression ratio as compared with other types of compressors while smoothly connecting suction, compression, and discharge strokes of a refrigerant, thereby obtaining a stable torque. Therefore, the scroll compressor is widely used for compressing refrigerant in an air conditioner, for example. Recently, a high-efficiency scroll compressor having a lower eccentric load and an operation speed at 180 Hz or higher has been introduced.
In general, a scroll compressor may be divided into a low pressure type in which a suction pipe communicates with an internal space of a casing constituting a low pressure portion, and a high pressure type in which a suction pipe directly communicates with a compression chamber. Accordingly, in the low pressure type, a drive unit s provided in a suction space which is the low pressure portion, whereas in the high pressure type, a drive unit is provided in a discharge space which is the high pressure portion.
Such a scroll compressor may be divided into an upper compression type and a lower compression type according to positions of the drive unit and the compression unit. A compressor in which the compression unit is located above the drive unit is referred to as an upper compression type, and a compressor in which the compression unit is located below the drive unit is referred to as a lower compression type.
In the scroll compressor, as a pressure of the compression chamber normally increases, an orbiting scroll is subjected to a gas force in a direction away from a fixed scroll. As the orbiting scroll then moves away from the fixed scroll, leakage between compression chambers occurs and compression loss increases.
In view of this, the scroll compressor employs a tip seal method in which a sealing member is inserted into an end face of each of a fixed wrap and an orbiting wrap, or a back pressure method in which a back pressure chamber forming an intermediate pressure or discharge pressure is formed on a rear surface of the orbiting scroll or the fixed scroll, and the orbiting scroll or the fixed scroll is pressed to an opposing scroll by the pressure of the back pressure chamber.
In particular, in the back pressure method, a sealing member is provided between the rear surface of the orbiting scroll (or the rear surface of the fixed scroll) and a frame corresponding thereto, such that the back pressure chamber is formed inside or outside the sealing member. In the back pressure method using such a sealing member, an annular groove is formed in one member consulting a thrust face, and an annular sealing member having a rectangular cross section is inserted into the annular groove. When the compressor is operated, a refrigerant of an intermediate pressure, compressed in the compression chamber, is introduced into the annular groove, and the sealing member is lifted by the intermediate pressure to be brought into close contact with an opposite member, so as to form the back pressure chamber.
However, in the related art scroll compressor as described above, back pressure applied to a central portion of the orbiting scroll becomes larger than back pressure applied to an edge portion of the orbing scroll, and thereby the central portion of the orbiting scroll is excessively pressed toward the fixed scroll. Then, a portion of the fixed wrap, adjacent to a discharge end, may excessively adhere to the orbiting scroll or a portion of the fixed wrap, adjacent to a discharge end, may excessively adhere to the fixed scroll. At the same time, the central portion of the fixed wrap or orbiting wrap is deformed while being bent outward due to a gas force and a centrifugal force applied in a direction of the edge portion, and thereby, frictional loss or abrasion may occur between the fixed wrap or the orbiting wrap and the scroll facing the same, causing a deterioration in compressor efficiency.
In the related art scroll compressor, in a case of a so-called shaft through scroll compressor in which a rotational shaft overlaps the compression chamber in a radial direction, as the rotational shaft is inserted through a central portion of the fixed scroll, a discharge end of the fixed wrap does not sufficiently extend up to the central portion of the fixed scroll due to the rotational shaft, and thereby, rigidity of the discharge end of the fixed wrap is weakened. Accordingly, the fixed wrap may be severely bent or the discharge end of the fixed wrap may be broken. Further, as disclosed in Korean Patent No. 10-1059880, which is hereby incorporated by reference, when a compression ratio of the compression chamber is increased by changing the fixed wrap and the orbiting wrap to an atypical shape, the discharge end of the fixed wrap may be further severely deformed and damaged. In addition, even when a protrusion is formed on the discharge and of the fixed wrap to increase a wrap supporting force, wrap deformation due to the increase in the compression ratio may not be completely suppressed, and thereby reliability of the compressor may be lowered due to frictional loss or abrasion or a wrap fracture.
In the related art scroll compressor, the deformation and fracture of the wrap (particularly, the fixed wrap) are suppressed by changing the shape of the wrap, as disclosed in Japanese Laid-Open Patent Publication No. 2000-257573, which is hereby incorporated by reference. However, in a case where roots of the wrap are made thick, the same groove should be formed on an end of the wrap of the opposite scroll, the wrap fabricating process becomes complicated, and a wrap thickness from a middle of the wrap to an end of the wrap is made thin. Accordingly, there is a limit in that the problem of deformation or fracture of the wrap cannot be solved.
Also, in view of this, when the wrap thickness is made thick as a whole, a size of the compressor is increased due to an increase in a size of the scroll for ensuring an orbiting radius, or a volume of the compression chamber is decreased due to a decrease of the orbiting radius. This may be seen as a result of arbitrarily changing the wrap shape without considering rigidity of the wrap.